Here is a general overview of how the body size of horses changed over time:
1. Eohippus (Eocene epoch):
- Size: Eohippus was a small animal, standing about 10-15 inches (25-38 cm) tall at the shoulder.
- Features: Eohippus had four toes on each forefoot and three toes on each hindfoot. It was herbivorous and adapted to forest environments.
2. Mesohippus (Oligocene epoch):
- Size: Mesohippus grew larger than Eohippus, reaching approximately 2-3 feet (60-90 cm) tall at the shoulder.
- Features: Mesohippus still had four toes on each forefoot and three toes on each hindfoot, but its legs and feet were becoming more adapted to running.
3. Merychippus (Miocene epoch):
- Size: Merychippus stood around 3-5 feet (90-150 cm) tall at the shoulder.
- Features: Merychippus had three toes on each foot and was well-adapted for running. It inhabited open grasslands and savannas.
4. Pliohippus (Pliocene epoch):
- Size: Pliohippus was larger than Merychippus, reaching approximately 5-7 feet (150-210 cm) tall at the shoulder.
- Features: Pliohippus had a single hoof on each foot, marking the transition from three-toed to single-toed animals. It continued to adapt for speed and endurance.
5. Equus (Pleistocene epoch to present):
- Size: The modern horse, belonging to the genus Equus, ranges in size depending on the breed. Some breeds, such as miniature horses, can stand as small as 28 inches (71 cm) at the shoulder, while larger breeds like the Shire horse can reach over 18 hands (72 inches or 183 cm) at the shoulder.
- Features: Modern horses have a single hoof on each foot, long legs, and a streamlined body for speed. They are herbivores, primarily consuming grasses and hay.
Throughout their evolution, horses gradually increased in size, with their legs and feet becoming longer and more specialized for running. The development of a single hoof from multiple toes provided them with greater speed and adaptability to different terrains. The body size of horses varied as they diversified into different species and adapted to various environments. Today's horses exhibit a wide range of sizes due to selective breeding by humans for specific purposes, including racing, transportation, and recreation.